The field of this disclosure relates generally to data reading systems, and more particularly to automated data reading systems where items are transported through a read zone of one or more data readers at which the items are identified by reading optical codes, RFID (radio frequency identification) tags, or other identifiers carried by the items.
Data reading systems are used to read optical codes, acquire data, and/or capture images to identify an item. Data reading devices are well known for reading UPC and other types of optical codes on packages, particularly in retail stores. One common data reader in such systems is an imaging reader that employs an imaging device or sensor array, such as a COD (charge coupled device) or CMOS (complementary metal oxide semiconductor) device. Imaging readers can be configured to read both 1-D and 2-D optical codes, as well as other types of optical codes or symbols and capture images of other items. When an imaging reader is used to read an optical code, an image of the optical code or portion thereof is focused onto a detector array. Though some imaging readers are capable of using ambient light illumination, an imaging reader typically utilizes a light source to illuminate the item being read to provide the required signal response in the imaging device.
An imager-based reader utilizes a camera or imager to generate electronic image data, typically in digital form, of an optical code. The image data is then processed to find and decode the optical code. For example, virtual scan line techniques are known techniques for digitally processing an image containing an optical code by looking across an image along a plurality of lines, typically spaced apart and at various angles, somewhat similar to the scan pattern of a laser beam in a laser-based scanner. It should be noted that a camera is typically a combination of a lens and an imaging device/sensor array, but the terms imager and camera may be used interchangeably herein.
Imager-based readers often can only form images from one perspective, usually that of a normal vector out of the face of the imager. Such imager-based readers therefore provide only a single point of view, which may limit the ability of the reader to recognize an optical code in certain circumstances. For instance, because the scan or view volume of an imager in an imager-based reader is typically conical in shape, attempting to read an optical code (e.g., a barcode) or other image in close proximity to the scanning window (reading “on the window”) may be less effective than with a basket-type laser scanner. Also, when labels are oriented such that the illumination source is reflected directly into the imager, the imager may fail to read properly due to uniform reflection washing out the desired image entirely, or the imager may fail to read properly due to reflection from a textured specular surface washing out one or more elements. This effect may cause reading of shiny labels to be problematic at particular reflective angles. In addition, labels oriented at extreme acute angles relative to the imager may not be readable. Lastly, the label may be oriented on the opposite side of the package with respect to the camera view, causing the package to obstruct the camera from viewing the barcode.
Thus, better performance could result from taking images from multiple perspectives. Imager-based readers that generate multiple perspectives are known. For example, one such reader is disclosed in U.S. Pat. No. 7,398,927, which describes an embodiment having two cameras to collect two images from two different perspectives for the purpose of mitigating specular reflection. In another example, U.S. Pat. No. 6,899,272 discloses a data reader that utilizes two independent sensor arrays pointed in different directions to collect image data from different sides of a package.
In some instances, scanning systems tend to use high-resolution, global shutter imagers/cameras to cover a wide field of view with high resolution. Such global shutter imagers tend to be expensive and increase the overall cost of the scanning system. In addition, in some multiple-camera imager-based readers, the system may require as many as ten, twelve, or even twenty individual cameras/imagers to adequately capture images from multiple perspectives. Each of these cameras/imagers typically requires illumination sources, circuit board(s), mounting hardware, and space for associated optical components. Such features and components typically increase the expense, complicate the physical design, and increase the overall size and bulk of the data reading system. The present inventors have, therefore, determined that it would be desirable to provide a data reading system with improved performance features and optical design configurations to minimize the number of individual cameras required to adequately capture multiple views of a target item, while maintaining a lean profile to minimize cost and size (e.g., bulk) of the data reading system.
Additional aspects and advantages will be apparent from the following detailed description of various example embodiments, which proceeds with reference to the accompanying drawings. Understanding that the drawings depict only certain embodiments and are not, therefore, to be considered limiting in nature, these embodiments will be described and explained with additional specificity and detail with reference to the drawings.